The present invention relates to an exterior rearview mirror assembly for mounting on a vehicle and, more particularly, to a break-away exterior rearview mirror assembly which moves between a normal operating position and a folded retracted position against the body of the vehicle when an external force is applied to the housing.
In most current vehicles, a typical exterior rearview mirror assembly includes a modular housing with a reflective element supported in the modular housing. The housing is supported on the vehicle or vehicle panel by a mounting bracket. To minimize the damage to the exterior rearview mirror assembly in the event of an impact with the mirror housing, auto manufacturers have designed mirror assemblies that fold or break-away about the mounting bracket under such an impact. This is achieved by pivotally mounting the modular housing to the mounting bracket on a pivot bushing and providing a plurality of radially extending detent assemblies which are formed on the mounting bracket and the housing. These detent assemblies releasably couple the housing to the mounting bracket under normal loading conditions but release the housing and permit the housing to pivot on the mounting bracket when the mirror housing is impacted by a force of sufficient magnitude.
Referring to FIG. 7, a conventional mounting bracket is shown. The mounting bracket includes a plurality of radially extending recesses or grooves, which cooperate with similarly arranged projections provided on the housing of the mirror assembly. The recesses are positioned around a central opening in the base of the mounting bracket which receives a pivot member or bushing. The projections are urged into engagement with the recesses on the mounting bracket by a spring, which is supported by the pivot member. In order to pivot the housing on the bracket and disengage the projections from the recesses provided on the mounting bracket, a force is required which has a sufficient magnitude to compress the spring and move the projections out of the corresponding recesses.
However, it is has been found that these conventional break-away devices tend to reduce the vibration performance of the exterior rearview mirror assembly. The detent assemblies are located around the medial portion of the mounting bracket, which is subject to maximum deflections. This allows movement and folding of the assembly with an undesirably low or inconsistent force. Furthermore, since the medial portion of the bracket is difficult to reinforce, the overall stiffness of the joint or connection is reduced. Therefore, the exterior rearview mirror exhibits increased vibration, resulting in reduced dampening performance. Moreover, the molding process for these conventional breakaway mirror assemblies requires a separate molding step for the recesses and ribs, since they are not aligned with the line of draw of the tooling.
Consequently there is a need for a break-away exterior rearview mirror assembly that exhibits increased stiffness and, therefore, improves the vibration characteristics of the exterior rearview mirror assembly. Furthermore, there is a need for a break-away device that can be molded in a single process along with the housing and the respective bracket to simplify the tooling, which will ultimately reduce the cost of manufacture.